1. Field of the Invention
The present invention relates to a device and method for providing secondary hydraulics in a downhole tool.
2. Background Art
“Full bore opening” safety valves have an opening through the valve that is substantially equal to the internal diameter of the attached tubing or completion string. The safety valves have a valve member therein (e.g. a rotatable ball or a pivoted flapper). The valve member may be shifted to its open position by an actuating sleeve that is axially mounted within the valve housing and operated by one or more hydraulic piston cylinders supplied by one or more control lines. The piston cylinder typically operates by shifting the actuating sleeve downward, resulting in the valve head moving into its open position. Pressurized control fluid for operating the piston cylinder is typically supplied from the surface by a hydraulic control line that communicates with a control fluid passage in the wall of the valve housing. When the valve is in the fully open position, the actuating sleeve is spring loaded and biased to move the valve into its closed position in the event of a loss of hydraulic control. A valve of this general type is disclosed in U.S. Pat. No. 4,716,969.
Various methods and systems have been designed to lock the valve member open in the event of any failure in the operation of the primary piston cylinder. In such an event, it is necessary to replace the defective safety valve with a functional safety valve. One typical manner of remediation, that one skilled in the art would appreciate, is to insert an in-tubing safety valve (or replacement safety valve) within the bore of the original defective safety valve while the original defective safety valve is locked in its, fully open position.
Such replacement valves are generally inserted by wireline, or slickline. The problem arises as to how the already installed hydraulic control line and hydraulic piston cylinder, sometimes referred to collectively by one skilled in the art as the “control fluid piping” or “control fluid conduit”, can be used to control the replacement safety valve.
U.S. Pat. No. 3,696,868 discloses an in-tubing replacement valve that may be installed in a defective safety valve, wherein the wall of the actuating sleeve of the defective valve is perforated prior to the insertion of the replacement valve in order to provide communication with the existing control fluid piping. A problem associated with this approach, that would be appreciated by one skilled in the art, stems from the possibility that perforating the originally installed safety valve sleeve may significantly damage the surrounding elements, including the exisiting hydraulic piston cylinder and/or the hydraulic control line.
Other prior art approaches to re-using the control line with the replacement safety valves use spare ports built into the original safety valve housing. These spare ports are closed with sealing elements or threaded plugs that can be removed by or after insertion of the replacement safety valve. However, a problem associated with this approach, that would be appreciated by one skilled in the art, stems from the possibility that the sealing element or threaded plug may leak or fail due to the high pressure, high temperature and/or caustic environment (e.g. in a well, or a pipeline). A similar device using this approach, disclosed in U.S. Pat. No. 3,799,258, proposes using a hollow, shearable, threaded nipple disposed in the wall of the original safety valve housing. The threaded nipple has an inwardly projecting end that may be sheared off by a sleeve that can be moved downwardly by a suitable tool conveyed through the tubing or completion string.
Although these prior art devices provide some ways to establish communication with an existing control fluid piping, there is a need for improved apparatus and methods for establishing such communication with less risk of leakage and/or damage to the surrounding elements.